sched: rotate the cpu search window for better spread

Rotate the cpu search window for better spread of threads. This will ensure
an idle cpu will quickly be found if one exists.

Orabug: 28482695
Signed-off-by: subhra mazumdar <[email protected]>
Reviewed-by: Rohit Jain <[email protected]>

Author: smazumda

kernel/sched/fair.c

@@ -5764,7 +5764,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
 	u64 avg_cost, avg_idle;
 	u64 time, cost;
 	s64 delta;
-	int cpu, limit, floor, nr = INT_MAX;
+	int cpu, limit, floor, target_tmp, nr = INT_MAX;
 
 	this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
 	if (!this_sd)
@@ -5795,9 +5795,15 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
 		}
 	}
 
+	if (per_cpu(next_cpu, target) != -1)
+		target_tmp = per_cpu(next_cpu, target);
+	else
+		target_tmp = target;
+
 	time = local_clock();
 
-	for_each_cpu_wrap(cpu, sched_domain_span(sd), target) {
+	for_each_cpu_wrap(cpu, sched_domain_span(sd), target_tmp) {
+		per_cpu(next_cpu, target) = cpu;
 		if (!--nr)
 			return -1;
 		if (!cpumask_test_cpu(cpu, &p->cpus_allowed))